VSB transmission system for processing supplemental transmission data

ABSTRACT

A VSB communication system or transmitter for processing supplemental data packets with MPEG-II data packets includes a VSB supplemental data processor and a VSB transmission system. The VSB supplemental data processor includes a Reed-Solomon coder for coding the supplemental data to be transmitted, a null sequence inserter for inserting a null sequence to an interleaved supplemental data for generating a predefined sequence, a header inserter for inserting an MPEG header to the supplemental data having the null sequence inserted therein, a multiplexer for multiplexing an MPEG data coded with the supplemental data having the MPEG header added thereto in a preset multiplexing ratio and units. The output of the multiplexer is provided to an 8T-VSB transmission system for modulating a data field from the multiplexer and transmitting the modulated data field to a VSB reception system.

CROSS REFERENCE TO RELATED ART

[0001] This application claims the benefit of Korean Patent ApplicationNo. 2000-83533, filed on Dec. 28, 2000, which is hereby incorporated byreference in their entirety.

[0002] This application incorporates by reference in their entiretyco-pending U.S. application Ser. No.______, mailed via Express Mail No.EF334462230US entitled “VSB COMMUNICATION SYSTEM” and Ser. No.______,mailed via Express Mail No. ET235110894US entitled “VSB RECEPTION SYSTEMWITH ENHANCED SIGNAL DETECTION FOR PROCESSING SUPPLEMENTAL DATA.”

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a digital televisiontransmission system, and more particularly, to a 8T-VSB (VestigialSideband) transmission system for transmitting supplemental data inaddition to MPEG data and to a signal format for the VSB transmissionsystem.

[0005] 2. Description of the Related Art

[0006] The United States of America has employed ATSC 8T-VSB (8Trellis-Vestigial Sideband) as a standard since 1995, and has beenbroadcasting in the ATSC 8T-VSB since the later half of 1998. SouthKorea also has employed the ATSC 8T-VSB as a standard. South Koreastarted test broadcasting in May 1995, and has since August 2000 put inplace a regular test broadcasting system. The advancement of technologyallows the transmission of digital television (DTV) in the same 6 MHzbandwidth currently used by NTSC.

[0007]FIG. 1 illustrates a block diagram of a related art ATSC 8T-VSBtransmission system (“VSB transmission system”). The VSB transmissionsystem 16 generally comprises a data randomizer 1, Reed-Solomon coder 2,data interleaver 3, Trellis coder 4, multiplexer 5, pilot inserter 6,VSB modulator 7 and RF converter 8.

[0008] Referring to FIG. 1, there is a data randomizer 1 for receivingand making random MPEG data (video, audio and ancillary data). The datarandomizer 1 receives the MPEG-II data output from an MPEG-II encoder.Although not shown in FIG. 1, the MPEG-II encoder takes baseband digitalvideo and performs bit rate compression using the techniques of discretecosine transform, run length coding, and bi-directional motionprediction. The MPEG-II encoder then multiplexes this compressed datatogether with pre-coded audio and any ancillary data that will betransmitted. The result is a stream of compressed MPEG-II data packetswith a data frequency of only 19.39 Mbit/Sec. The MPEG-II encoderoutputs such data to the data randomizer in serial form. MPEG-II packetsare 188 bytes in length with the first byte in each packet always beingthe sync or header byte. The MPEG-II sync byte is then discarded. Thesync byte will ultimately be replaced by the ATSC segment sync in alater stage of processing.

[0009] In the VSB transmission system 16, the 8-VSB bit stream shouldhave a random, noise-like signal. The reason being that the transmittedsignal frequency response must have a flat noise-like spectrum in orderto use the allotted 6 MHz channel space with maximum efficiency. Randomdata minimizes interference into analog NTSC. In the data randomizer 1,each byte value is changed according to known pattern of pseudo-randomnumber generation. This process is reversed in the VSB receiver in orderto recover the proper data values.

[0010] The Reed-Solomon coder 2 of the VSB transmission system 16 isused for subjecting the output data of the data randomizer 1 toReed-Solomon coding and adding a 20 byte parity code to the output data.Reed Solomon encoding is a type of forward error correction schemeapplied to the incoming data stream. Forward error correction is used tocorrect bit errors that occur during transmission due to signal fades,noise, etc. Various types of techniques maybe used as the forward errorcorrection process.

[0011] The Reed-Solomon coder 2 takes all 187 bytes of an incomingMPEG-II data packet (the sync or header byte has been removed from 188bytes) and mathematically manipulates them as a block to create adigital sketch of the block contents. This “sketch” occupies 20additional bytes which are added at the tail end of the original 187byte packet. These 20 bytes are known as Reed-Solomon parity bytes. The20 Reed-Solomon parity bytes for every data packet add redundancy forforward error correction of up to 10 byte errors/packet. SinceReed-Solomon decoders correct byte errors, and bytes can have anywherefrom 1 to 8 bit errors within them, a significant amount of errorcorrection can be accomplished in the VSB receiver. The output of theReed-Solomon coder 2 is 207 bytes (187 plus 20 parity bytes).

[0012] The VSB receiver will compare the received 187 byte block to the20 parity bytes in order to determine the validity of the recovereddata. If errors are detected, the receiver can use the parity bytes tolocate the exact location of the errors, modify the corrupted bytes, andreconstruct the original information.

[0013] The data interleaver 3 interleaves the output data of theReed-Solomon coder 2. In particular, the data interleaver 3 mixes thesequential order of the data packet and disperses or delays the MPEG-IIpacket throughout time. The data interleaver 3 then reassembles new datapackets incorporating small sections from many different MPEG-II(pre-interleaved) packets. The reassembled packets are 207 bytes each.

[0014] The purpose of the data interleaver 3 is to prevent losing of oneor more packets due to noise or other harmful transmission environment.By interleaving data into many different packets, even if one packet iscompletely lost, the original packet may be substantially recovered frominformation contained in other packets.

[0015] The VSB transmission system 16 also has a trellis coder 4 forconverting the output data of the data interleaver 3 from byte form intosymbol form and for subjecting it to trellis coding. Trellis coding isanother form of forward error correction. Unlike Reed-Solomon coding,which treated the entire MPEG-II packet simultaneously as a block,trellis coding is an evolving code that tracks the progressing stream ofbits as it develops through time.

[0016] The trellis coder 4 adds additional redundancy to the signal inthe form of more (than four data levels, creating the multilevel (8)data symbols for transmission. For trellis coding, each 8-bit byte issplit up into a stream of four, 2-bit words. In the trellis coder 4,each 2-bit input word is compared to the past history of previous 2-bitwords. A 3-bit binary code is mathematically generated to describe thetransition from the previous 2-bit word to the current one. These 3-bitcodes are substituted for the original 2-bit words and transmitted asthe eight level symbols of 8-VSB. For every two bits that enter thetrellis coder 4, three bits come out.

[0017] The trellis decoder in the VSB receiver uses the received 3-bittransition codes to reconstruct the evolution of the data stream fromone 2-bit word to the next. In this way, the trellis coder follows a“trail” as the signal moves from one word to the next through time. Thepower of trellis coding lies in its ability to track a signal's historythrough time and discard potentially faulty information (errors) basedon a signal's past and future behavior.

[0018] A multiplexer 5 is used for multiplexing a symbol stream from thetrellis coder 4 and synchronizing signals. The segment and the fieldsynchronizing signals provide information to the VSB receiver toaccurately locate and demodulate the transmitted RF signal. The segmentand the field synchronizing signals are inserted after the randomizationand error coding stages so as not to destroy the fixed time andamplitude relationships that these signals must possess to be effective.The multiplexer 5 provides the output from the trellis coder 4 and thesegment and the field synchronizing signals in a time division manner.

[0019] An output packet of the data interleaver 3 comprises the 207bytes of an interleaved data packet. After trellis coding, the 207 bytesegment is stretched out into a baseband stream of 828 eight levelsymbols. The segment synchronizing signal is a four symbol pulse that isadded to the front of each data segment and replaces the missing firstbyte (packet sync byte) of the original MPEG-II data packet. The segmentsynchronizing signal appears once every 832 symbols and always takes theform of a positive-negative-positive pulse swinging between the +5 and−5 signal levels

[0020] The field synchronizing signal is an entire data segment that isrepeated once per field. The field synchronizing signal has a known datasymbol pattern of positive-negative pulses and is used by the receiverto eliminate signal ghosts caused by poor reception.

[0021] The VSB transmission system 16 also has the pilot inserter 6 forinserting pilot signals into the symbol stream from the multiplexer 5.Similar to the synchronizing signals described above, the pilot signalis inserted after the randomization and error coding stages so as not todestroy the fixed time and amplitude relationships that these signalsmust possess to be effective.

[0022] Before the data is modulated, a small DC shift is applied to the8T-VSB baseband signal. This causes a small residual carrier to appearat the zero frequency point of the resulting modulated spectrum. This isthe pilot signal provided by the pilot inserter 6. This gives the RF PLLcircuits in the VSB receiver something to lock onto that is independentof the data being transmitted.

[0023] After the pilot signal has been inserted by the pilot inserter 6,the output is subjected to a VSB modulator 7. The VSB modulator 7modulates the symbol stream from the pilot inserter 6 into an 8 VSBsignal of an intermediate frequency band. The VSB modulator 7 provides afiltered (root-raised cosine) IF signal at a standard frequency (44 Mhzin the U.S.), with most of one sideband removed.

[0024] In particular, the eight level baseband signal is amplitudemodulated onto an intermediate frequency (IF) carrier. The modulationproduces a double sideband IF spectrum about the carrier frequency. Thetotal spectrum is too wide to be transmitted in the assigned 6 MHzchannel.

[0025] The sidelobes produced by the modulation are simply scaled copiesof the center spectrum, and the entire lower sideband is a mirror imageof the upper sideband. Therefore using a filter, the VSB modulatordiscards the entire lower sideband and all of the sidelobes in the uppersideband. The remaining signal (upper half of the center spectrum) isfurther eliminated in one-half by using the Nyquist filter. The Nyquistfilter is based on the Nyquist Theory, which summarizes that only a ½frequency bandwidth is required to transmit a digital signal at a givensampling rate.

[0026] Finally, there is a RF (Radio Frequency) converter 8 forconverting the signal of an intermediate frequency band from the VSBmodulator 7 into a signal of a RF band signal, and for transmitting thesignal to a reception system through an antenna 9.

[0027] The foregoing VSB communication system is at least partiallydescribed in U.S. Pat. Nos. 5,636,251, 5,629,958 and 5,600,677 by ZenithCo. which are incorporated herein by reference. The 8T-VSB transmissionsystem, which is employed as the standard digital TV broadcasting inNorth America and South Korea, was developed for the transmission ofMPEG video and audio data. As technologies for processing digitalsignals develop and the use of the Internet increases, the trendcurrently is to integrate digitized home appliances, the personalcomputer, and the Internet into one comprehensive system.

[0028] Therefore, in order to satisfy the variety of the demands ofusers, there is a need to develop a communication system thatfacilitates the addition and transmittal of a variety of supplementaldata to the video and audio data through the digital broadcastingchannel. It is predicted that the use of supplemental data broadcastingmay require PC (Personal Computer) cards or portable appliances, withsimple indoor antennas.

[0029] However, there can be a substantial reduction of signal strengthdue to walls and nearby moving bodies. There also can be ghost and noisecaused by reflective waves, which causes the performance of the signalof the supplemental data-broadcasting to be substantially poor.Supplemental data broadcasting is different from general video and audiodata in that it requires a lower error ratio in transmission. Forgeneral video and audio data, errors imperceptible to the human eye orear are inconsequential. In contrast, for supplemental data, even onebit of error in the supplemental data (which may include programexecution files, stock information, and other similar information) maycause a serious problem. Therefore, the development of a communicationsystem that is more resistant to the ghost and noise occurring on thechannel is absolutely required.

[0030] In general, the supplemental data is transmitted by a timedivision system on a channel similar to the MPEG video and audio data.After the incorporation of digital broadcasting, there has already beena widespread emergence in the home appliance market of receiversequipped to receive ATSC VSB digital broadcast signals. These productsreceive NDEG video and audio data only. Therefore, it is required thatthe transmission of supplemental data on the same channel as the MPEGvideo and audio data has no adverse influence on the existing receiversthat are equipped to receive ATSC VSB digital broadcasting.

[0031] The above situation is defined as ATSC VSB backwardcompatibility, and the supplemental data broadcasting system must be asystem that is backward-compatible with the ATSC VSB communicationsystem.

SUMMARY OF THE INVENTION

[0032] Accordingly, the present invention is directed to a VSBcommunication system, and a signal format for the VSB communicationsystem that substantially obviates one or more of the problems due tothe limitations and disadvantages of the related art.

[0033] An object of the present invention is to provide an ATSC VSBtransmission system, which can transmit the present MPEG video and audiodata together with supplemental data.

[0034] Another object of the present invention is to provide an ATSC VSBtransmission system that is more robust to ghost and noise.

[0035] A further object of the present invention is to provide a newATSC VSB transmission system that is fully backward-compatible with arelated art ATSC VSB transmission system.

[0036] A still further object of the present invention is to provide atransmission data format that is suitable to an ATSC VSB transmissionsystem which is robust to ghost and noise.

[0037] Additional features and advantages of the invention will be setforth in the description that follows, and in part will be apparent fromthe description, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0038] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, theVSB transmitter for use with an MPEG data signal and a supplemental datasignal comprises a VSB supplemental data processor and a 8TVSBtransmission system. The VSB supplemental data processor comprises aforward error correction coder that codes the supplemental data signal;a null sequence inserter for inserting a null sequence to thesupplemental data signal subjected to the forward error correction coderfor generating a predefined sequence; a header inserter for inserting aheader to the supplemental data signal having the null sequence insertedtherein; and a multiplexer for multiplexing the MPEG data signal and thesupplemental data signal having the header inserted thereto in at leastone of a predetermined multiplexing ratio and unit.

[0039] The VSB transmission system is responsive to the VSB supplementaldata processor for modulating an output from the multiplexer to form atleast one data field comprising a plurality of segments that includes atleast one segment representing the supplemental data signal and at leastone segment representing the MPEG data signal.

[0040] According to one aspect of the present invention, the forwarderror correction coder is a Reed-Solomon coder. The supplemental datasignal includes at least one data packet having X bytes and theReed-Solomon coder provides parity bytes of Y bytes, wherein a total ofX and Y bytes is 184 bytes.

[0041] According to another aspect of the present invention, the headerinserter adds three bytes of header information to the data packet.Preferably, the null sequence inserter divides the one data packet ofthe supplemental data signal into two data packets. The predefinedsequence has substantially the same occurrence of bits “1” and “0”.

[0042] According to another aspect of the present invention, the VSBtransmitter further comprises an interleaver receiving data from theforward error correction coder and outputting to the null sequenceinserter. The interleaver interleaves the supplemental data signal withforward error corrected code.

[0043] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

[0045]FIG. 1 illustrates a block diagram showing a conventional VSBtransmission system;

[0046]FIG. 2 illustrates a block diagram showing a VSB transmitter fortransmitting supplemental and MPEG data in accordance with a preferredembodiment of the present invention;

[0047]FIG. 3 illustrates the frame architecture of a transmission datafor a VSB transmission system in accordance with a preferred embodimentof the present invention;

[0048]FIG. 4 illustrates a diagram showing a process for multiplexingsupplemental data and MPEG data for forming a VSB data field;

[0049]FIG. 5 illustrates an example of inserting the null sequence intothe supplemental data by the null sequence inserter and generating apredefined sequence;

[0050]FIG. 6 illustrates a schematic diagram of a data interleaver forinterleaving supplemental data;

[0051]FIG. 7 illustrates an example of coding supplemental data; and

[0052]FIG. 8 illustrates another example of coding supplemental data.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0054]FIG. 2 illustrates a block diagram showing a VSB transmitter 110for the transmission of the supplemental and MPEG data in accordancewith a preferred embodiment of the present invention. FIG. 3 illustratesthe frame architecture of transmission data for a VSB transmissionsystem in accordance with a preferred embodiment of the presentinvention. FIG. 4 illustrates a diagram showing a process formultiplexing supplemental data and MPEG data for forming a VSB datafield. FIG. 5 illustrates a diagram showing a process for inserting anull sequence to generate a predefined sequence. FIG. 6 illustrates adiagram showing a data interleaver for interleaving supplemental data.FIG. 7 illustrates a diagram showing an example of coding supplementaldata, and FIG. 8 illustrates a diagram showing another example of codingsupplemental data.

[0055] In FIG. 2, the VSB transmitter 110 in accordance with a preferredembodiment of the present invention includes a VSB supplemental dataprocessor 100 and a VSB transmission system 16. The description of theVSB transmission system 16 is described above in connection with FIG. 1,and thus, will not be repeated. According to the preferred embodiment ofthe present invention, the VSB supplemental data processor includes aReed-Solomon coder 11, a data interleaver 12, a null sequence inserter13, an MPEG header inserter 14, a multiplexer 15, an 8TVSB transmissionsystem 16, and an antenna 17.

[0056] As shown in FIG. 2, for the transmission of the supplemental datafrom the VSB transmitter 110 (i.e., a broadcasting station) to a VSBreception system on a channel (terrestrial or cable), the VSBtransmitter 110 subjects the supplemental data to various digital signalprocesses. To provide backward compatibility of the present inventionwith existing devices, the supplemental data is preferably 164 bytepacket which will eventually be processed to be a 187 byte packet beforeentering the VSB transmission system 16. However, the size of thesupplemental data packet may be varied so long as the output of the VSBsupplemental data processor 100 is compatible with the VSB transmissionsystem 16.

[0057] In the VSB supplemental data processor 100, there is provided aReed-Solomon coder 11 for the correction of errors. The supplementaldata is coded at a Reed-Solomon coder (or R-S coder) 11. Preferably, theReed-Solomon coder 11 is used for subjecting the supplemental data toReed-Solomon coding and adding a 20 byte parity code to the output data.As described above, Reed Solomon encoding is a type of forward errorcorrection scheme applied to the incoming data stream. Forward errorcorrection is used to correct bit errors that occur during transmissiondue to signal fades, noise, etc. Various other types of error correctiontechniques known to one of ordinary skill in the art may be used as theforward error correction process.

[0058] According to the preferred embodiment, the Reed-Solomon coder 11of the VSB supplemental data processor takes 164 bytes of an incomingsupplemental data packet and mathematically manipulates them as a blockto create a digital sketch of the block contents. The 20 additionalbytes are added at the tail end of the original 164 byte packet. These20 bytes are known as Reed-Solomon parity bytes. Since Reed-Solomondecoders of the VSB reception system correct byte errors, and bytes canhave anywhere from 1 to 8 bit errors within them, a significant amountof error correction can be accomplished in the VSB receiver. The outputof the Reed-Solomon coder 11 is preferably 184 bytes (164 bytes from theoriginal packet plus 20 parity bytes).

[0059] The VSB supplemental data processor 100 further includes the datainterleaver 12, which interleaves the output data of the Reed-Solomoncoder 11. The data interleaver 12 is for interleaving the codedsupplemental data to enhance performance against burst noise. The datainterleaver 12 may be omitted, if necessary.

[0060] The data interleaver 12 according to the preferred embodimentmixes the sequential order of the supplemental data packet and dispersesor delays the supplemental data packet throughout time. The datainterleaver 12 then reassembles new data packets incorporating smallsections from many different supplemental data packets. Each one of thereassembled packets are 184 bytes long.

[0061] As described above, the purpose of the data interleaver 12 is toprevent losing of one or more packets due to noise or other harmfultransmission environment. By interleaving data into many differentpackets, even if one packet is completely lost, the original packet maybe recovered from information contained in other packets. However, thereis a data interleaver in the ATSC 8T-VSB transmission system, the datainterleaver for the supplemental data can be omitted if it is notrequired to enhance the burst noise performance of the supplementaldata. For this reason, the data interleaver 12 may not be necessary forthe VSB supplemental data processor 100.

[0062] The VSB supplemental data processor 100 also includes the nullsequence inserter 13 for inserting a null sequence to an allocatedregion of the interleaved (if the data interleaver 12 was present) orReed-Solomon coded supplemental data for generating the predefinedsequence for the supplemental data at an input terminal of a Trelliscoder (shown in FIG. 1). The null sequence is inserted so that the VSBreception system receives the supplemental data more reliably, even in anoisy multipath fading channel. An example structure of the transmissiondata formed by the insertion of the null sequence will be explainedbelow in detail with reference to FIG. 5.

[0063] Further referring to FIG. 2, the VSB supplemental data processor100 includes the MPEG header inserter 14 for adding an MPEG header tothe supplemental data having the null sequence inserted thereto, forbackward-compatibility with the legacy VSB reception system. Because theMPEG-II data supplied to the VSB transmission system 16 is 187 byteslong, the MPEG header inserter 14 places, preferably, three headers infront of each packet (which was 184 bytes) to form a 187 byte longpacket identical to the MPEG-II data packet.

[0064] The supplemental data having the MPEG header added thereto isprovided to a multiplexer 15. The multiplexer 15 receives as inputs theprocessed supplemental data from the MPEG header inserter 14 and MPEGdata packets. MPEG data packet, such as a broadcasting program (movie,sports, entertainment, or drama), coded through another path (outputfrom MPEG encoder), is received together with the supplemental data atthe multiplexer 15. Upon reception of the BPEG data and the supplementaldata, the multiplexer 15 multiplexes the supplemental data and the MPEGdata at a fixed ratio under the control of a controller defining amultiplexing ratio and unit and forwards the multiplexed data to the8T-VSB transmission system 16.

[0065] The 8T-VSB transmission system 16, which is described in detailin reference to FIG. 1, processes the multiplexed data and transmits theprocessed data to the VSB reception system through the antenna 17.

[0066] For example, the Reed-Solomon coder 11 uses a code having a blocksize N=184, a payload K=164, and an error correction capability T=10. Onthe other hand, as a polynomial generator of the Galois Field and theReed-Solomon coder 11, the same code as the Reed-Solomon coder 2described with respect to FIG. 1 may be used. According to the preferredembodiment, other values of the block size N, the payload K, and theerror correction capability T may be used in the Reed-Solomon coder 11in FIG. 2. For an example, a code having N=184, K=154, and T=15 may beused, or a code having N=92, K=82, and T=5 may be used. Although theReed-Solomon code is used in the present invention, other code suitablefor error correction known to one of ordinary skill in the art may beused therein.

[0067]FIG. 3 illustrates the structure of a VSB data field used in theVSB transmission system 100. As shown in FIG. 3, one data field has 313segments: 312 data segments 124 and one field synchronizing segment 122.The 312 data segments have data segments of the supplemental data andthe MPEG data segments. Each data segment 124A has 184 byte data, a 3byte MPEG header, and the 20 byte ATSC Reed-Solomon parity. The 3 byteMPEG header will used by the MPEG decoder in the VSB reception system.

[0068] The use of the MPEG header is explained in more detail. ISO/IEC13818-1 has a definition on an MPEG transport packet header. If a 0×47synchronization byte is removed from the MPEG transport packet header, a3 byte header is left. A PID (program identification) is defined by this3 bytes. A transport part of the MPEG decoder discards a packet if thePID of the received packet received is not valid. For example, a nullpacket PID or other reserved PID can be used. Therefore, the MPEG headerinserter 14 in FIG. 2 inserts the 3 byte header containing such a PIDinto the supplemental data packet. Therefore, the supplemental data canbe discarded at the MPEG decoder of the legacy VSB receiver.

[0069]FIG. 4 illustrates a process for multiplexing the supplementaldata and the MPEG data at the multiplexer 15 in FIG. 2. As shown in FIG.4, the supplemental data is multiplexed with the MPEG data in segmentunits. The supplemental data is multiplexed with the MPEG data insynchronous to the field synchronizing signal used for synchronizing adata frame synchronization in the VSB transmission system.

[0070] Therefore, the VSB reception system determines the multiplexinglocations of the MPEG data and the supplemental data in the field datareceived synchronous to the field synchronizing signal. The VSBreception system demultiplexes the MPEG data and the supplemental databased on the multiplexing locations. A multiplexing ratio and method formultiplexing the MPEG data and the supplemental data may vary withamounts of data thereof.

[0071] Information on the variable multiplexing method and ratio may beloaded on, for example, a reserved area of the 92 bits not used in thefield synchronizing signal. By retrieving and decoding such information,the VSB reception system identifies the correct multiplexing ratio andmethod from the multiplexing information contained in the fieldsynchronizing signal.

[0072] Alternatively, the multiplexing information may be inserted, notonly in the reserved area of the field synchronizing signal, but also inthe data segment of the supplemental data. As shown in FIG. 4, of theentire 312 multiplexed data segments, one half are occupied by the datasegments representing the supplemental data inputted to the VSBsupplemental data processor 100. One of the supplement data segment maybe used to transmit the multiplexing information for use by the VSBreception system.

[0073]FIG. 5 illustrates an example of inserting the null sequence intothe supplemental data by the null sequence inserter 13 according to thepreferred embodiment of the present invention. The supplemental datahaving the null sequence inserted therein is transmitted to the VSBreception system. The predefined sequence has 1's and 0's arranged in afixed order. The predefined sequence inserted in the supplemental datacan be used for performance improvement in the reception system.

[0074] For example, the channel equalizer of the VSB reception systemuses the sequence to enhance ghost cancellation performance of both thesupplemental data and the MPEG data and the Trellis decoder can use thesequence to improve noise performance of supplemental data. As shown inFIG. 5, upon reception of one supplemental data byte, the null sequenceinserter 13 for generating the predefined sequence inserts null bits, toprovide two bytes.

[0075] The inserted null sequence is processed in the VSB transmissionsystem 16 in FIG. 2, and then transmitted to the VSB reception system.The null sequence is randomized by the data randomizer 1 of the VSBtransmission system 16, and coded by the Reed-Solomon coder 2. Then, thenull sequence is interleaved by the data interleaver 3, and provided tothe Trellis coder 4 as an input signal D0. This converted sequence isthe predefined sequence. The input signal D0 is a lower bit of the twoinput bits to the Trellis coder 4. The Trellis coder is basicallyoperative such that three bits are provided with two received bits.

[0076] The VSB reception system generates the sequence received as theinput signal D0 from the Trellis coder in the 8T-VSB transmission system16, i.e., the predefined sequence, and uses the generated sequence forimproving its own performance. Alternatively, other sequences known toone of ordinary skill in the art may be used instead of the nullsequence described above.

[0077] The VSB transmitter 110 of the present invention is required tohave identical probabilities of occurrence of the 8 levels, for havingbackward-compatibility with the related art VSB transmission system.Therefore, the presence of the 0's and 1's in the sequence received asthe input signal D0 at the Trellis coder are required to be almost thesame.

[0078]FIG. 6 illustrates a block diagram of the data interleaver 12 forinterleaving the supplemental data in FIG. 2. According to the preferredembodiment, a convolutional interleaver may be used as the datainterleaver 12. However, other suitable interleaver, such as a blockinterleaver, known to one of ordinary skill in the art may also be used.

[0079] Referring to FIG. 6, the data interleaver 12 has ‘B’ (preferably46) branches, and ‘M’ (preferably 4) bytes of unit memory. The datainterleaver 12 may be operative synchronous to a field synchronizationsignal of the VSB transmission system 16. The ‘B’ branches, and the ‘M’bytes of unit memory of the data interleaver 12 may be changed to othersuitable value without deviating from the gist of the present invention.

[0080] Because the VSB transmission system 16 already includes a datainterleaver 3, as shown in FIG. 1, the data interleaver 12 in the VSBsupplemental data processor 100 of FIG. 2 may be omitted if no furtherburst noise performance improvement is required.

[0081]FIG. 7 illustrates a block diagram showing an example ofsupplemental data coding according to the preferred embodiment of thepresent invention. Referring to FIG. 7, the supplemental data has ablock size of 164 bytes. FIG. 7 illustrates the process of coding thesupplemental data packet until the supplemental data packet is providedto the multiplexer 15. This occurs after the supplemental data packetpasses the Reed-Solomon coder 11, the data interleaver 12, the nullsequence inserter 13, and the MPEG header inserter 14 in FIG. 2 insuccession.

[0082] The operation of the VSB supplemental data processor 100according to the present invention will be described. According to FIG.7, a Reed-Solomon 20 byte parity is inserted to the supplemental datathat is 164 bytes long by the Reed-Solomon coder 11. This processchanges the supplemental data into a 184 byte packet. A number of paritybytes may vary with a number of the supplemental data bytes. Forexample, if the supplemental data has 154 bytes, the parity has 30bytes. At the end, the number of the supplemental data bytes having theparity bytes added thereto is fixed to be 184 bytes in advance. Thesupplemental data having the parity added thereto is interleaved by thedata interleaver 12 and provided to the null sequence inserter 13 92bytes by 92 bytes. The null sequence inserter 13 inserts 92 bytes of thenull data into each of the 92 bytes of supplemental data to provide two184 byte packets for the 184 bytes of supplemental data, where the 20parity bytes are included in only one of the two 184 byte packets.

[0083] Thereafter, the MPEG header inserter 14 inserts 3 bytes of MPEGheader, preferably containing the PID, to the front part of each of thesupplemental data packets for backward-compatibility with the relatedart ATSC 8T-VSB transmission system. The multiplexer 15 multiplexes eachof the supplemental data packets from the MPEG header inserter 14 andthe MPEG data received through another route, and transmits themultiplexed data to the VSB transmission system 16. The VSB transmissionsystem 16 codes the multiplexed data and transmits the data to the VSBreception system.

[0084]FIG. 8 illustrates a diagram showing another example of coding thesupplemental data. Referring to FIG. 8, 10 bytes of parity bits areinserted into the 82 extra bytes by the Reed-Solomon coder 11, to changethe extra bytes into a 92 byte packet. The number of parity bytes varieswith the number of the supplemental data bytes. That is, if thesupplemental data has 72 bytes, then the parity has 20 bytes. At theend, the supplemental data having the parity added thereto is fixed tohave 92 bytes in advance. The 92 bytes of supplemental data having the10 bytes of parity added thereto is interleaved by the interleaver 12,and provided to the null sequence inserter 13, and the null sequenceinserter 13 inserts 92 bytes of null sequence into the 92 bytes ofsupplemental data, to provide a total 184 bytes of packet. Accordingly,each of the 184 bytes of packets includes 10 parity bytes.

[0085] Similar to FIG. 7, the MPEG header inserter 14 inserts 3 bytes ofMPEG header to the front part of the 184 bytes of supplemental datapackets for backward-compatibility with the related art ATSC 8T-VSBtransmission system, for a total of 187 bytes of data. Finally, themultiplexer 15 multiplexes each of the supplemental data packets fromthe MPEG header inserter 14 and MPEG data received through anotherroute, and transmits the multiplexed data to the VSB transmission system16. The VSB transmission system 16 codes the multiplexed data, andtransmits the data to the VSB reception system. At the end, FIGS. 7 and8 are identical in that the total number of bytes of the supplementaldata having the null sequence inserted thereto is 184, and the totalnumber of bytes of the supplemental data having the MPEG header addedthereto is 187.

[0086] As has been explained, the present invention has the followingadvantages. First, supplemental data can be transmitted on the samechannel with MPEG data with the supplemental data multiplexed with theMPEG data.

[0087] Second, a backward-compatibility with the conventional ATSC 8TVSB system can be sustained. That is, the reception of the MPEGtransport data at the ATSC 8T-VSB receiver is not affected. Third,reliable reception both of the MPEG data and the supplemental data atthe reception system is facilitated by using the predefined sequenceinserted in the supplemental data even on a channel with excessiveghost. Fourth, a noise immunity of the supplemental data is enhanced atthe VSB reception system by using the predefined sequence inserted inthe supplemental data. Fifth, transmission of other MPEG data throughsupplemental data path is permitted, which in turn permits reception ofthe MPEG data even in a poor channel state.

[0088] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the VSB communicationsystem, and the signal format for the VSB communication system of thepresent invention without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

What is claimed is:
 1. A VSB transmitter for use with an MPEG datasignal and a supplemental data signal, the VSB transmitter comprising: aVSB supplemental-data processor comprising: a forward error correctioncoder that codes the supplemental data signal; a null sequence inserterfor inserting a null sequence to the supplemental data signal subjectedto the forward error correction coder for generating a predefinedsequence; a header inserter for inserting a header to the supplementaldata signal having the null sequence inserted therein; and a multiplexerfor multiplexing the MPEG data signal and the supplemental data signalhaving the header inserted thereto in at least one of a predeterminedmultiplexing ratio and unit; and a VSB transmission system connected tothe VSB supplemental data processor for modulating an output from themultiplexer to form at least one data field comprising a plurality ofsegments that includes at least one segment formed from the supplementaldata signal and at least one segment formed from the MPEG data signal.2. The VSB transmitter of claim 1, wherein the forward error correctioncoder is a Reed-Solomon coder.
 3. The VSB transmitter of claim 2,wherein the supplemental data signal includes at least one data packethaving X bytes and the Reed-Solomon coder provides parity bytes of Ybytes, wherein a total of X and Y bytes is 184 bytes.
 4. The VSBtransmitter of claim 3, wherein the header inserter adds three bytes ofheader information to the data packet, wherein the header informationcontains program identification.
 5. The VSB transmitter of claim 3,wherein the null sequence inserter divides the one data packet of thesupplemental data signal into a plurality of data packets.
 6. The VSBtransmitter of claim 5, wherein the predefined sequence hassubstantially the same occurrence of bits “1” and “0”.
 7. The VSBtransmitter of claim 1, further comprising an interleaver receiving datafrom the forward error correction coder and outputting to the nullsequence inserter, the interleaver interleaves the supplemental datasignal coded by forward error correction code.
 8. The VSB transmitter ofclaim 7, wherein the forward error correction coder is a Reed-Solomoncoder.
 9. The VSB transmitter of claim 8, wherein the supplemental datasignal includes at least one data packet having X bytes and theReed-Solomon coder provides parity bytes of Y bytes, wherein a total ofX and Y bytes is 184 bytes.
 10. The VSB transmitter of claim 9, whereinthe header inserter adds three bytes of header information to the datapacket, wherein the header information contains program identification.11. The VSB transmitter of claim 9, wherein the null sequence inserterdivides the one data packet of the supplemental data signal into aplurality of data packets.
 12. The VSB transmitter of claim 11, whereinthe predefined sequence has substantially the same occurrence of bits“1” and “0”.
 13. The VSB transmitter of claim 1, wherein themultiplexing unit is a segment, and the multiplexing ratio varies withamounts of MPEG data packets representing the MPEG data signal andsupplemental data packets representing the supplemental data signal. 14.The VSB transmitter of claim 13, wherein the multiplexing ratio of thesupplemental data packets and the MPEG data packets in the multiplexeris one segment to one segment.
 15. The VSB transmitter of claim 13,wherein the multiplexing ratio of the supplemental data packets and theLEG data packets in the multiplexer is one segment to three segments.16. The VSB transmitter of claim 1, wherein the multiplexer isresponsive to a field synchronizing signal used for synchronizing a dataframe of the VSB transmission system.
 17. The VSB transmitter of claim1, wherein the data field has 312 data segments and one fieldsynchronizing segment.
 18. A VSB supplemental data processor for usewith a VSB transmission system to provide a supplemental data signal andan MPEG data signal thereto, wherein the VSB transmission systemmodulates at least one data field comprising a plurality of segmentsthat includes at least one segment formed from the supplemental datasignal and at least one segment formed from the MPEG data signal, theVSB supplemental data processor comprising: a forward error correctioncoder that codes the supplemental data signal; a null sequence inserterfor inserting a null sequence to the supplemental data signal subjectedto the forward error correction coder for generating a predefinedsequence; a header inserter for inserting a header to the supplementaldata signal having the null sequence inserted therein; and a multiplexerfor multiplexing the MPEG data signal and the supplemental data signalhaving the header inserted thereto in at least one of a predeterminedmultiplexing ratio and unit.
 19. The VSB supplemental data processor ofclaim 18, wherein the forward error correction coder is a Reed-Solomoncoder.
 20. The VSB supplemental data processor of claim 19, wherein thesupplemental data signal includes at least one data packet having Xbytes and the Reed-Solomon coder provides parity bytes of Y bytes,wherein a total of X and Y bytes is 184 bytes.
 21. The VSB supplementaldata processor of claim 20, wherein the header inserter adds three bytesof header information to the data packet, wherein the header informationcontains program identification.
 22. The VSB supplemental data processorof claim 20, wherein the null sequence inserter divides the one datapacket of the supplemental data signal into a plurality of data packets.23. The VSB supplemental data processor of claim 22, wherein thepredefined sequence has substantially the same occurrence of bits “1”and “0”.
 24. The VSB supplemental data processor of claim 18, furthercomprising an interleaver receiving data from the forward errorcorrection coder and outputting to the null sequence inserter, theinterleaver interleaves the supplemental data signal with forward errorcorrected code.
 25. The VSB supplemental data processor of claim 24,wherein the forward error correction coder is a Reed-Solomon coder. 26.The VSB supplemental data processor of claim 25, wherein thesupplemental data signal includes at least one data packet having Xbytes and the Reed-Solomon coder provides parity bytes of Y bytes,wherein a total of X and Y bytes is 184 bytes.
 27. The VSB supplementaldata processor of claim 26, wherein the header inserter adds three bytesof header information to the data packet, wherein the header informationcontains program identification.
 28. The VSB supplemental data processorof claim 26, wherein the null sequence inserter divides the one datapacket of the supplemental data signal into a plurality of data packets.29. The VSB supplemental data processor of claim 28, wherein thepredefined sequence has substantially the same occurrence of bits “1”and “0”.
 30. The VSB supplemental data processor of claim 18, whereinthe multiplexing unit is a segment, and the multiplexing ratio varieswith amounts of MPEG data packets representing the MPEG data signal andsupplemental data packets representing the supplemental data signal. 31.The VSB supplemental data processor of claim 30, wherein themultiplexing ratio of the supplemental data packets and the MPEG datapackets in the multiplexer is one segment to one segment.
 32. The VSBsupplemental data processor of claim 30, wherein the multiplexing ratioof the supplemental data packets and the MPEG data packets in themultiplexer is one segment to three segments.
 33. A method for asupplemental data packet and an MPEG data packet in a VSB transmittercomprising a VSB supplemental data processor and a VSB transmissionsystem, the method comprising the steps of: subjecting the supplementaldata packet of preset bytes to a Reed-Solomon coding and adding aReed-Solomon parity data of preset bytes to the supplemental datapacket; interleaving the coded supplemental data packet; inserting nullsequence data into the interleaved supplemental data packet forproducing at least one supplemental data packet of a preset number ofbytes; adding an MPEG header of preset bytes to each one of thesupplemental data packets; multiplexing the MPEG data packet with thesupplemental data packet at a preset multiplexing ratio; and modulatingthe data multiplexed at the preset multiplexing ratio through the VSBtransmission system.
 34. The method claim 33, wherein the Reed-Solomonparity is included to only one of the supplemental data packets.
 35. Themethod of claim 33, wherein the inserting null sequence data includesthe steps of; dividing the supplemental data packet into twosupplemental data packets having the same numbers of bytes; andinserting a null sequence having the same bytes with the supplementaldata packet into each one of the supplemental data packets to providetwo supplemental data packets each having the null sequence insertedtherein.
 36. The method of claim 35, wherein each one of thesupplemental data packets has 184 bytes comprising 92 bytes ofsupplemental data 92 bytes of the null sequence.
 37. The method of claim33, wherein the MPEG header is an identification code for identifyingwhether the multiplexed data is the supplemental data packet or the MPEGdata packet.
 38. A VSB signal format comprising: an MPEG header region;and a supplemental data region having original supplemental data andnull sequence data.
 39. The VSB signal format of claim 38, wherein theMPEG header region has 3 bytes, the original supplemental data has 92bytes, and the null sequence data has 92 bytes.
 40. The VSB signalformat of claim 38, wherein the supplemental data region furtherincludes a Reed-Solomon parity of preset bytes.